Coalition troops, including 9,500 British, will on Saturday surpass the nine years and fifty days which the Red Army spent unsuccessfully trying to build a socialist state.

The milestone comes as Nato has 140,000 troops deployed in the country and levels of violence are at their highest since the US-backed ousting of the Taliban in October 2001.

Russian troops invaded Afghanistan on December 27, 1979, to prop up a communist regime facing a popular uprising.

On February 15, 1989, the last armoured convoy of wearied Russian forces retreated north across the Amu Darya river into Uzbekistan after failing to quell a CIA-backed resistance which Mikhail Gorbachev had labelled "our bleeding wound".

Mohammad Najibullah, the puppet leader the Soviet's left behind, clung onto power for another three years until he was ousted by the Mujahideen rebels.

Nato's special forces-led mission in the wake of the September 11 attacks to topple the Taliban and kill or capture their al Qaeda terrorist guests, has grown into a vast counter-insurgency campaign.

Nine years after the Taliban fled to their Pakistan havens, the resurgent movement controls swathes of the south and Nato is losing on average 50 to 60 troops a month.

Generals say they have this summer finally reversed the insurgents' momentum, but a Pentagon assessment this week said progress was patchy.

Wadir Safi, a professor at Kabul University and minister in the Najibullah government, said "the Americans never reached the goal for which they came."

"If they don't change their policy, if they don't reach their goals, if they don't reach agreement with the armed opposition and with the government, then it is not a far time that the Afghan people will be fed up with the presence of these foreign forces." Nader Nadery, an Afghan analyst who has studied the both invasions, said the Nato presence could not be compared with the brutality of the Red Army occupation.

As the Soviets lost control of the countryside to rebels backed by hundreds of millions of pounds from America and the Gulf states, they resorted to indiscriminate campaigns of bombing and massacre. More than a million civilians died.

He said: "There was indiscriminate mass bombardment of villages for the eviction of Mujahideen. Civilian casualties are not at all comparable."